A cellarium (from the Latin cella, "pantry"), also known as an undercroft, was a storehouse or storeroom, usually in a medieval monastery or castle. In English monasteries, it was usually located in or under the buildings on the west range of the cloister.^[1]

The monastery's supplies of food, ale and wines were stored there, under the supervision of the cellarer, one of the monastery's obedientiaries. He was often assisted by a sub-cellarer.^[2]